This section provides background information related to the present disclosure that may or may not include prior art.
Oligomers are useful components in curable compositions such as coating compositions. Oligomers can be used in coating systems, for example, as diluents or curing agents that undergo reaction under cure conditions to form a cured, crosslinked film. One problem with making oligomers has been producing oligomers of consistent identity, molecular weight, or both due to the variety of oligomers that can be formed when using polyfunctional reactants. Primarily simplistic systems of linear oligomers formed from difunctional reactants have been attempted. Work using trifunctional or even higher functionality reactants has produced gelled materials with other polyfunctional materials. It is difficult to make an oligomer composition with a consistent make-up from batch to batch due to the inherent difficulty is controlling the multiple reactions that can occur simultaneously when using multi-functional reactants. Protecting groups can be one way to address issues such as this but their removal generally requires an additional reaction step and in many instances an additional purification step. In addition, a lack of selectivity among the various functional groups toward the capping compound results unavoidably in a mixture of products, including those in which all functional groups are blocked and those in which an insufficient number of functional groups are blocked, resulting consequently in a distribution of species in the final product.
Accordingly, there remains a need in the art for methods of reliably and consistently forming oligomers of more consistent identity. In addition, oligomers may be useful in coating compositions if oligomer identity and molecular weight are such that properties of the coating composition like volatile organic content, cure temperature, and physical cured film properties are improved by incorporating the oligomer.